Django:实现读写分离

库的配置

1.读写分离

• settings配置

#settings.py 配置库信息，生成2个库

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    },
    'db2': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db2.sqlite3'),
    },
}

python3 manage.py makemigrations   #生成迁移文件
python3 manage.py migrate --database db2 #db2数据库迁移

• 手动操作

ret = model.Student.objects.all().using('db2')#查询db2库所有数据

models.Student.object.using("default").create(name='xxoo')#往default库写入信息

#db2查询name='ss'，并更改name,并保存在default库中
obj = models.Stundet.objects.using('db2').get(name='ss')
obj.name = "sha"
obj.save(using="default")

• 自动操作

#myrouter.py

class Router:
	def db_for_write(self,model,**kwargs):
		return "db2"

	def db_for_read(self,model,**kwargs):
		return "default"
#settings.py配置
DATABASE_ROUTERS=['myrouter.Router',]

2.一主多从

#myrouter.py

class Router:
	def db_for_write(self,model,**kwargs):
		return "default"

	def db_for_read(self,model,**kwargs):
		return random.choice(['db2','db3',"db4"])
#settings.py配置
DATABASE_ROUTERS=['myrouter.Router',]

3.分库分表

• 分库：

#settings.py配置
#myrouter.py
class Router:
    """
    app01   model  db1
    app02   model  db2
    """
	def db_for_write(self,model,**kwargs):
         app_name = model._meta.app_label#此操作能获得app的名字
         if app_name == "app01":
            return "db1"
        elif app_name == "app02":
			return "app02"

	def db_for_read(self,model,**kwargs):
		app_name = model._meta.app_label#此操作能获得app的名字
        if app_name == "app01":
            return "db1"
        elif app_name == "app02":
			return "app02"

4.Django执行原生SQL

• 单起一个文件

import os
import django
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "temp.settings")
djnago.setup()
#以上配置django环境

#extra方法：
from app01 import models
#从Student，找id大于1的对象值
ret = models.Student.object.all().extra(where=['id>%s'],params=['1']).values()
print(ret)

#raw方法：
ret = models.Student.objects.raw('select * from main.app01_classes')
print(ret)
for i in ret:
    print(i)#拿到学生对象
#connection方法：
from django.db import connections
#cursor = connections.cursor()
cursor = connections['db2'].cursor()#指向db2库
cursor.execute("""select * from main.app_classes where id=%s""",[1,])
row = cursor.fetchall()
print(row)